Protective device for electric heaters.



c. C. NUCKOLS.

PROTECTIVE DEVICE FOR ELECTRIC HEATERS.

APPLICATION FILED OCT. 3, I914- ,v-r

Patented Oct. 31,1916.

2 $HEETSSHEET I.

6 unllmm WITNESSES:

C. C. NUCKOLS.

PROTECTIVE DEVICE FOR ELECTRIC. HEATERS.

APPLICATION FILED OCT. 3, 1914. 1,203,125. Patented Oct. 31,1916.

2 SHEETSSHEET 2 R O T E V N I S E S E N I W 1g {52W 0/0111? dJ z'wZv/s',

,/M/Mw I BY I i I ATTY UNITED STATES PATENT OFFICE.

CLAUDE C. NUCKOLS, OF ALBANY, NEW YORK, ABSIGNOB TO CONSOLIDATED CAB- HEATING COMPANY, 01 ALBANY, NEW YORK, A CORPORATION 01 WEST VIR- GINIA.

PROTECTIVE DEVICE FOR ELECTRIC HEATERS.

Specification of Letters Patent.

Patented Oct. 31, 1916.

Application filed October 3, 1914. Serial No. 884,841.

T 0 all whom it may concern Be it known that I, CLAUDE C. N cKoIs, a citizen of-the United States, residing at Albany, county of Albany, and State of New York, have invented certain new and useful Improvements in Protective Devices for Electric Heaters, the following being a full, clear, and exact disclosure of the one form of my invention which I at present deem preferable.

For a detailed description of the present form of my invention, reference ma be had to the followin specification an to the accompanying rawings, forming a part thereof, wherein- Figure 1 is a diagram of the circuits; Figs. 2 and 3 show the details of one form of my device; Figs. 4 and 5 show a slight modification.

My invention relates to the protection of I an electric heater against excessive temperatures. In the first place I provide a thermal rotector, such as a fuse, placed within the heater-casing and included in the electric circuit which contains the heater-coils. This fuse will be subjected to the heating eflect ,lating within the casing and will therefore respond to an excessive degree of such heat in the casing even though the current which flows through it at the time does not exceed a safe amount. For example, the outflow of heated air from the casing may be obstructed by a ladys dress for a long time, and the heat in the casing will there ore accumulate to such an extent that the fuse will be thereby melted, even if the current in it is of the normal value. The advantage of such a device is that the heater is protected not only from an excessive amount of current in its coils, but also from the accumulation of generated heat in the casing. On the other hand a fuse located as I have just described is liable, when it acts,

while the heater current is still of normal value. By this means the heater circuit will still be broken, in the event of an undue accumulation of heat in the casing, although the heater current remains of normal value and the outside fuse does not,'of itself, take cognizance of the heat in the casin The current will, of course, divide itself Eetween the two fuses in inverse ratio to their respective resistances but the casing-fuse will be so adjusted that, in the event of an abnormal current passing through it, said casing-fuse will be ruptured by the abnormal current before that portion of the said current which passes through the external fuse is sufficient to equal the total value of the normal current-in the heater coils. In the event of an undue accumulation of heat in the casing, the casing-fuse will also be ruptured by the accumulated heat within the casing, whereas the external fuse will remain intact, since the latter is not exposed with the metal of the casing because the casin -fuse is shunted by the external fuse,

and t e current will pass through the external fuse after the casing fuse is melted. The external fuse will then act under the abnormal current to finally break the circuit and, since it is located out of proximity to the heater casing, it will do so without danger of grounding on the casing.

Referring to the diagram in Fig. 1, H, H, etc., represent tWo groups of electric heater coils, it being understood that each group will be inclosed in a casing as is customary and constitute an ordinary electric-heater unit. The two groups of coils are in parallel with each other between the trolley T on one side and the ground G on the other side, it being assumed for illustration that the heaters are utilized for car heating. The circuit from trolley T passes through the switch S and the usual fuse F, and then branches between the two groups of heater coils, going to ground at G. F represents the casing-fuse to which I have heretofore referred, it being included in the circuit of one of the groups of heater coils, being placed, for example, in the center of one coil H. The fuse F is shunted by the external fuse F which is located outside of and away from proximity to the heater coils in any convenient place. These fuses F and F will be related to each other and will act as I have heretofore described.

Referring to Figs. 2 and 3, G is the porcelain core of an ordinary electric heater, the coils H being in the form of spirals wound in a spiral groove on the outside surface of core C. At the center of core C the grooves are interrupted and the cylindrical core is there embraced by two metal bands K, K which form the terminals of the two portions of coil H located respectively on either side of the bands K, K. Between the bands K, K is extended the casing-fuse F being secured thereto by screw-clamps, and from the said bands also extend-the Wires P, P leading to the external fuse F at'a suitable distance from the heater. In Figs. 4.- and 5 the arrangement is the same except that an annular disk K of insulating material is employed in place of the two bands K, K. The fuse F is extended between two binding screws on the disk K a suitable distance apart, and from the same binding screws the wires P, P lead to the external fuse F What I claim as new and desire to secure casing heater,

heater, of a thermal protector in circuit with the heater coils and responsive to an over generation of heat within the heater and also responsive to an excess current, and a second thermal protector also in circuit with the heater coils and in parallel with the first thermal protector, the second thermal protector being responsive only to excess current and positioned to act as a final circuit breaker after the first protector has operated.

3. The combination with an electric of a thermal protector therefor located in the heater casing and in circuit with the heater coils, and a second thermal protector in parallel with the first one located outside of the heater casing.

4. The combination with an electric heater, of a thermal protector therefor located in proximity thereto and responsive to either an excessive heater-current or to an excessive accumulation of generated heat, and a second thermal protector in parallel with the first one and responsive to normal heater-current upon the action of the first device in response to either excessive current or excessive heat.

5. The combination with an electricheater core, of coil terminals thereon, a fuse connected between said terminals in proximity to the coils, and leads connecting said terminals with a second fuse located at a distance from said coils.

6. The combination with a plurality of electric heaters connected in parallel to the circuit, of a fuse in said circuit in series with all the heaters, a local fuse at each heater responsive to either an excess of current or to an excess of coil-generated heat, and a fuse in parallel with each of said local 1flus'es but not sub ected to said coil-generated eat.

In witness whereof I have hereunto set my hand, before two subscribing witnesses, this 30th day of September, 1914.

CLAUDE C. NUOKOLS. Witnesses:

JOHN A. B. MCELVENEY, FRANK M. Roos. 

